Not Applicable
Not Applicable
Not Applicable
Movement of articles vertically between decks of a ship or floors of a building may be accomplished by vertical conveyor, which lifts or lowers shelves onto which the articles are placed. The shelves are suspended via one or more endless chains, which are driven by engaged sprockets. To reduce space requirements, it is desirable to pivot the shelves from the horizontal load carrying position to a vertical return position while the shelves travel along the return path of the endless chain(s). Stability of the shelves is highly desirable for conveying purposes. Rollers riding within tracks may accomplish control of the motion of individual shelves, both for stability and during the transition from horizontal to vertical.
Existing technology for vertical conveyors employ tilting shelves. The individual shelves are held horizontally during the working portion of their travel, and tilted to vertical for the return portion of travel. As such, the shelves are orientation sensitive, i.e. one side of the shelf is the top, and the other is the bottom. Control of the tilting motion of the shelves is usually accomplished by the use of two pairs of rollers, rigidly attached to the each end of the shelves, riding within guide tracks. Such tilting shelf conveyors, such as shown in U.S. Pat. No. 2,747,724 issued May 29, 1956 and U.S. Pat. No. 3,365,052 issued Jan. 29, 1968 employ tracks with either a crossover pattern or a cusp-section to temporarily halt and redirect a roller. Both methods are subject to jamming as rollers can engage the wrong track, or bypass the cusp section, when they are inadequately constrained within these transition zones. Additionally, the tracks are difficult to manufacture and expensive, due to the exacting tolerances required to minimize jamming.
The present invention simplifies the mechanism of shelf motion control of vertical conveyors by allowing the shelves to be reversible rather than tilting, thus orientation insensitive. This results in reduced construction costs, and significantly greater reliability.
Control of shelf motion is provided by a pair(s) of rollers, rigidly fixed to one or both ends of each shelf, which ride within a straight channel track during the lifting phase, and straddle a straight track bar during the return phase. At the terminal ends of the lifting phase, the rollers exit the channel track while simultaneously the shelf itself comes into contact with the sprocket drum, causing it to rotate to parallel with the chain. Continued rotation of the sprocket reverses the direction of travel of the shelf, and the pair(s) of rollers then straddle the track bar for the return phase. Shelves entering the lift phase exit the sprocket drum before one of the rollers contacts the end of the channel track. Continued travel of the chain causes the shelf to rotate to the horizontal position, followed by both rollers entrance into the channel track.